camber dependant leak

[loftus.hall]

So I have a mystery leak that I have traced to the passenger side C pillar on a hatchback with a sunroof.
The mystery is that it doesn't leak when parked so the passenger side is higher than the driver side.
When it leaks it seems to pour in, faster than if it were coming in through gaps around the sunroof which has a pretty good seal as I refitted and cleaned it up a while ago before it was leaking.
I took it through the car wash and even bubles of soap seemed to come through! The headlining of the car doesn't get wet either, the water appears out of the bottom of the plastic trim that covers the panel that early bx's had a small window in instead, then flows down behind the back seat ending up under the seat above the fuel tank in a small puddle.

Planning to remove the plastic trim panel at the rear to investigate further but the pace the water comes in makes me think there should be quite a sizeable hole but on the outside there isn't anything obvious.
Could it be under the roof trim panel that runs down the side of the roof? Can that be sealed from underneath if the roof lining is pulled down?
Or could the door seals be the fault and if so is there a good way to check them?
Any advice much appreciated.
Other than this there's nothing wrong with it, (which considering it's over 200k now is great) so would be nice to solve this!

[sdelasal]

I had a problem where rain water seemed to flow into the actual door seal, where it clamps onto the bodywork. The water then ran down the door seal and exited inside the car under the rear seat and into the floor as well. I cured it with using sealant into the seal - the horizontal section at the top of the door aperature, then popping it back onto the bodyshell. Trying removing the door real below the door lock area and see f it is wet. Steve

[JayW]

It's almost certainly the sunroof drain pipe, there is one at each corner.

Just to clarify, the sunroof doesn't actually seal properly, that is why the headlining is designed as a tray with the drains.

Alternatively, as mentioned above, dodgy door seal or hole under the gutter trim.

[rutter123]

Each corner of the headlining tray has a drain tube which lets excess water drain away to the ground, generally what happens is little bits of crap, silt, leaves and the like build up and block the top of the drain tubes. These can be accessed via the inside a pillar just in front of the front doors pull the trim away and you will find a clear tube about 1/2 inch in diameter pull this thru and blow an airline or similar up it this should dislodge any crap collected at the top. As for the rear drain tubes these can be accessed by removal of the rear light clusters if you fish around behind them you will find the same plastic tubes, again pull them through and blow the airline up them. The BX sunroof is NOT a watertight unit and is designed to let water into the headlining tray to drain via the 4 tubes, usually the front ones block and water will pour in just above the front doors ultimately causing rust issues in the a pillars and floor if left untreated, most BX owners suffer this at some point. Make this a once yearly job and you should remain dry on the inside, telltale signs of the rear tubes being blocked is puddles of water in the rear footwells, hope this helps.